The invention relates to an air dryer cartridge for a compressed air treatment system of a vehicle, in particular of a commercial vehicle, having a spring cover and a support element which together, in the assembled state of the air dryer cartridge, define a volume of the air dryer cartridge. A drying agent (desiccant) box is provided, which is arranged within the volume and which is filled with a drying agent. The spring cover and the support element are designed as cylinders substantially closed off on one side, at the open ends of which the spring cover and the support element can be coupled.
The invention also relates to a method for producing an air dryer cartridge for a compressed air treatment system of a vehicle, in particular of a commercial vehicle, wherein the air dryer cartridge includes a spring cover and a support element which together, in the assembled state of the air dryer cartridge, define a volume of the air dryer cartridge, and wherein a drying agent box which is filled with a drying agent is arranged within the volume.
The invention still further relates to a compressed air treatment system for a vehicle, in particular a commercial vehicle, having an air dryer cartridge according to the invention.
Air dryer cartridges are required within the context of the provision and treatment of compressed air for compressed air treatment systems, EAC for short, in particular in the commercial vehicle field. There, the air dryer cartridges are used for removing oil and dirt particles from the generated compressed air, and for drying the compressed air. Such air dryer cartridges are considered “wear parts” since they must be occasionally replaced.
An air dryer cartridge known from the prior art is illustrated in FIG. 1. The air dryer cartridge 10 shown is composed substantially of a drying agent box (also called a “desiccant box”) 20, which is filled with a drying agent (also called a “desiccant”) 38 and which is arranged in a spring cover 16. The spring cover 16 is closed off in the lower region by a base plate 42 with an air inlet 50 and an air outlet 52. The base plate 42 and the spring cover 16 are fixedly connected to one another by way of a flanged seam 56. An O-ring 44 and a sealing ring 40 with a rubber lip 48 provide sealing between the base plate 42 and the drying agent box 20, wherein the rubber lip 48 operates as a check valve.
The sealing ring 40 is mechanically or chemically connected to the drying agent box 20, wherein the rubber lip 48 has a defined opening and closing characteristic. In particular, the rubber lip 48 opens in the event of an excess pressure in the air dryer cartridge 10, and thus acts as a safety valve. The drying agent box 20 is delimited in its axial direction of extent by a first air filter 30 and a second air filter 32, which retain the drying agent 38 in the interior of the drying agent box 20.
Furthermore, in the upper region of the air dryer cartridge 10, there is arranged a compression spring 34 and a granulate cover 36, by which the drying agent 38 in the interior of the drying agent box 20 is compressed. The granulate cover 36 is, in particular, designed to be air permeable.
A combination filter, for example in the form of a coalescence filter 26, extends in the axial direction around the lower half of the drying agent box 20 and is fixed in the radial direction to a supporting structure 54 of the drying agent box 20 by a sleeve 28. The coalescence filter 26 divides the air dryer cartridge 10 into a pre-filter region and a post-filter region. It is the object of the coalescence filter 26 during a compressed air delivery phase to retain oil and dirt particles and also emulsion droplets on an incident-flow surface, to store liquid oil, and by means of a coalescence effect to convert extremely fine oil droplets and aerosols into liquid oil and separate out said oil. Here, the design of the outflow surface and the filter construction yield a defined ratio of air outflow speed and oil droplet size. This ratio ensures that no oil droplets pass via the post-filter region into the drying agent box 20 and thus shorten the service life of the air dryer cartridge 10 and downstream consumers.
Air guiding elements 46 project in the radial direction from the drying agent box 20 into the coalescence filter 26 and prevent the inflowing air from bypassing the coalescence filter 26. The sealing between the pre-filter region and the post-filter region during a compressed air delivery phase is thus realized by way of a special sealing geometry composed of air guiding elements 46 in conjunction with the sleeve 28 at the outside.
The coalescence filter 26 is wound in the azimuthal direction around the drying agent box 20, in particular on the supporting structure 54 which is permeable to air and which is part of the drying agent box 20. Here, the filter material of the coalescence filter 26 forms at least one filter layer in the radial direction. The sleeve 28, which may be formed for example as an elastic rubber sleeve, fixes the filter material of the coalescence filter 26 in the radial direction. At the same time, the sleeve 28 allows the coalescence filter 26 to breathe during the accumulation of oil and dirt particles within the filter material, and protects the coalescence filter 26 against destruction. The filter material of the coalescence filter 26 directly adjoins the drying agent box 20.
Furthermore, EP 0 230 991 A2 discloses an air dryer cartridge in which the housing parts of the air dryer cartridge are connected to one another by means of a snap-action connection which comprises a circlip.
Furthermore, U.S. Pat. No. 4,838,901 A and DE 198 27 566 A1 each disclose an air filter, the housings of which are, respectively, closed off by at least one flexible pair of “shoulders and posts” and joined together by means of a snap-action connection.
It is an object of the present invention to simplify the construction of an air dryer cartridge.
This and other objects are achieved by an air dryer cartridge for a compressed air treatment system of a vehicle, in particular of a commercial vehicle, having a spring cover and a support element which together, in the assembled state of the air dryer cartridge, define a volume of the air dryer cartridge. A drying agent box is provided which is arranged within the volume and which is filled with a drying agent. The spring cover and the support element are designed as cylinders substantially closed off on one side, at the open ends of which are arranged a snap-action connection by which the spring cover and the support element can be coupled. The snap-action connection element on the spring is encompassed on both sides perpendicular to an axial direction by the snap-action connection element on the support element.
As a result of the encompassment at both sides, the snap-action connection provides an adequate sealing action, such that an additional seal between the spring cover and the support element for sealing off the housing of the air dryer cartridge can be dispensed with. All the parts of the air dryer cartridge, in particular the necessary parts, are clamped between the spring cover and the support element. The parts of the air dryer cartridge include, for example, a granulate cover, a compression spring, a drying agent box, an air filter in the form of a nonwoven filter, drying agent, a check valve and a small O-ring. The compact cartridge unit can be easily removed from the compressed air treatment system, and exchanged, as a unit. The releasable snap-action connection allows the spring cover, the support element and further parts of the air dryer cartridge to be re-used, while worn parts, in particular the drying agent and filter nonwovens, can be exchanged.
It may preferably be provided that a coalescence filter is wound on the drying agent box and is fixed by a sleeve. The winding of the coalescence filter on the drying agent box makes it possible to dispense with a support device, which is separate from the drying agent box and which positions the coalescence filter within the air dryer cartridge at the side remote from the drying agent box.
It is particularly preferable for air filters to be arranged on an upper end and on a lower end of the drying agent box. The drying agent present in the interior of the drying agent box can be prevented from exiting the drying agent box by means of the air filters.
It may be provided that a granulate cover which is braced with respect to the spring cover by a compression spring fixes the drying agent in the drying agent box. In this way, the drying agent, which is usually present as granulate in the drying agent box, can be kept as densely packed as possible, wherein drying agent losses which occur through natural wear can be compensated by a reduction in size of the provided volume, in order to maintain the dense packing.
It may also be provided that the support element and the drying agent box are produced in one piece. This permits a “direct” coupling of the spring cover to the drying agent box without further components, such that the construction of the air dryer cartridge as a whole is simplified.
In the described method, it may be provided that the spring cover and the support element are coupled by a snap-action connection.
This also applies to the particularly preferred embodiments of the described method.
The method may in particular be refined in that a coalescence filter is wound on the drying agent box and fixed by a sleeve.
It may advantageously be provided that, before the filling of the drying agent box with drying agent, a first air filter is arranged at a lower end of the drying agent box, and that after the filling of the drying agent box with drying agent, a second air filter is arranged at the top end of the drying agent box.
It may also be provided that the drying agent is fixed in the drying agent box by a granulate cover, which is braced with respect to the spring cover by a compression spring.
It may also be provided that the support element and the drying agent box are produced in one piece.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.